Phosphorylazido phospholipids will be synthesized and studied as a new class of photochemical affinity reagents for lipid-protein polar binding interactions. These new probes will be used to explore questions of structure and mechanism in Phospholipase A2 (PLA2). PLA2 is a enzyme of wide occurrence involved in phospholipid metabolism and has been specifically linked to prostaglandin biosynthesis, digestion of food lipids, the biosynthesis of pulmonary lung surfactant, and a variety of other processes. Our initial work will concentrate on several purified PLA2 enzymes and will address questions concerning enzyme structure and the chemical mechanisms for catalysis.